In current human and animal medical practice, there are numerous instances where therapeutic agents must be delivered to a specific organ or a tissue within the body. An example is the infusion of chemotherapy into a central vein on a recurring basis over a lengthy treatment period for widespread sites of malignant tumor. Without an access device for intravenous drug infusion, multiple vein punctures over a lengthy period would result in progressive thrombosis, venous sclerosis, and destruction of small diameter peripheral vessels. In other cases, it may be desirable to infuse chemotherapy to a localized malignant tumor site. It may be difficult or impossible to deliver an agent specifically to such a site on a regular repetitive basis without surgically implanting an access system. Similarly, repeated arterial access is occasionally needed for injection of an X-ray dye or contrast agent into an artery for diagnostic purposes. In other situations, there is a need to repetitively remove a body fluid for analysis from a remote body site. Finally, sensing and physiological measuring devices incorporated into small diameter catheters and small diameter optical fibers are increasingly being utilized for monitoring body processes and could be more easily implemented through a properly designed access device with an adequate internal diameter.
In prior medical practice, percutaneous catheters have been used to provide vascular or organ access for drug therapy or the withdraw of body fluids. Although such systems generally performed in a satisfactory manner, numerous problems were presented by such therapy approaches, including the substantial care requirements of the patients, e.g. dressing changes with sterile techniques, a significant rate of infection of the catheter because of its transcutaneous position, and a high rate of venous thrombosis, particularly if the catheter was located within an extremity vein.
Implantable infusion devices or "ports" have recently become available and represent a significant advance over transcutaneous catheters. Presently available infusion ports have a number of common fundamental design features. The ports themselves comprise a housing which forms a reservoir that can be constructed from a variety of plastic or metal materials. A surface of the reservoir is enclosed by a high-density, self-sealing septum, typically made of silicone rubber. Connected to the port housing is an internal catheter which communicates with a vein or other site within the patient where the infusion of therapeutic agents is desired. Implantation of such devices generally proceeds by making a small subcutaneous pocket in an appropriate area of the patient under local anesthesia. The internal catheter is tunneled to the desired infusion site. When the care provider desires to infuse or remove materials through the port, a hypodermic needle is used which pierces the skin over the infusion port and is placed into the port.
Although the presently available implantable infusion ports generally operate in a satisfactory manner, they have a number of shortcomings. Since these devices rely on a compressed rubber septum for sealing and since large diameter needles can seriously damage the septum, there are limitations in the diameter of needles which can be used to penetrate the septum. Also, the needles are randomly inserted to penetrate the septum, producing a cut or puncture wound, partially consuming and destroying the septum with each penetration. The diameter limitations severely restrict the flow rate of fluids passing through the port. In cases where it is desirable to infuse drugs using a flexible external catheter, the catheter must be fed through the needle that penetrates the septum. Such catheters have an extremely small inside diameter and, therefore, impose severe limitations on fluid flow rate.
During prolonged infusion using a conventional port, the infusion needle is taped to the patients skin to hold it in position. Conventional ports do not allow the needle to penetrate deeply into the port. Because of this, a small displacement of the needle can cause it to be pulled from the port. In cases where locally toxic materials are being infused, extravasation of such materials can cause local tissue damage which may require corrective surgery such as skin grafting or removal of tissue.
Presently available implantable drug infusion devices also have a significant size to provide an acceptable target surface area for the care provider who must locate the port and penetrate the septum with a needle. The port housing becomes bulky as the septum size increases since structure is required to maintain the septum in compression to provide self-sealing after the needle is removed. Moreover, presently available infusion ports are difficult to clear if thrombosis occurs within the port or within the implanted internal catheter since it is difficult, if not impossible, to feed a cleaning wire through the penetrating hypodermic needle in a manner which will clear the infusion device and the internal catheter. Present infusion ports also have a retained volume beneath the self-sealing septum which increases the volume of drug which must be administered to enable a desired quantity to reach the infusion site. This retained volume also poses problems when a care provider desires to successively deliver multiple drugs to the same infusion site which are incompatible when mixed. Additionally, when it is desired to withdraw blood through the port, the retained volume of the prior art infusion ports comprises an area where blood clotting can occur, thus interfering with future access to the site. And finally, for present infusion ports, there is a risk that the care provider attempting to pierce the port septum will not properly enter it, leading to the possibility of extravasation which can cause significant undesirable consequences as mentioned above.
The present invention relates to a family of implantable access ports which provide numerous enhancements over prior art devices. In accordance with this invention, an access port is provided which incorporates the funnel-shaped entrance orifice which narrows down to a reduced diameter passageway. The passageway retains a valve. One characteristic of valves used with the present invention is that the valves are not physically damaged or destroyed by the passage of a filament through the valve. In this regard, the valve can be referred to as being a "non-destructive" valve. Another characteristic of the valves intended to be used with the present invention is that they are constructed to be repetitively engaged by the filament in a predetermined location. Generally , this location is the center of the valve. Valves which meets the above criteria are referred to as "articulating catheter valves" or "articulating valves", such as a multi-element leaflet valve assembly. After the valve, the passageway is connected to an implanted internal catheter.
Several embodiments of this invention are intended to be used by inserting an instrument such as a needle, trocar or other introducer through the skin into a port entrance orifice which introduces a filament, such as a catheter, into the port. While some embodiments of this invention are used with blunt introducers, other embodiments of the present invention are adapted to be used in conjunction with a sharp hypodermic access needle of conventional design which may be used by itself for infusion or fluid withdrawal, or with an external catheter having the needle fed through it (or vise versa) allowing the catheter to be put in position within the access port or fed into the implanted catheter for infusion or withdrawal of fluid. The entrance orifice has a hard surface which guides the needle to a guide passageway. The reduced diameter guide passageway of the port housing can be used to accurately align the access needle and/or catheter to strike the articulating valve at a desired area. In this manner, a needle can be used to pass through the catheter valve repeatedly without damaging the function of the valve.
According to another group of embodiments of this invention, additional features of access ports are described. One area of potential improvement for some purposes is the provision of a port designed for implantation in a patient's arm which has an access passageway for an inserted needle. The body of this port is slightly angled upward to facilitate access. Such an angled access port can also feature modifications to the entrance orifice to again further enhance the ability to access the implanted port. This application further describes a valving concept for an implanted port which provides a high degree of resistance to body fluid leakage through the port and which further provides a relatively low level of friction upon insertion of an external catheter and a relatively higher degree of friction upon withdrawal of the catheter. This difference in resistance aids both in inserting of the catheter and in maintaining the catheter in an inserted condition within the implanted port.
This specification also describes port design features which are best embodied in a port in which the entrance funnel is in a plane generally parallel to the mounting base of the port (i.e. the accessing needle penetrates perpendicular to the mounting base). One improvement for such ports is the provision of a physical feature such as a projecting lug, flange or other protuberance which enables the clinician to determine the orientation of the implanted port through tactile examination. By knowing the port orientation, the needle and introduced filament can often be more readily inserted into the port. This series of ports, known as "chest wall" ports (named for a preferred usage), also feature a funnel-shaped entrance orifice having a progressively changing included angle. The orifice starts at its outer periphery with a relatively shallow included angle which increases toward the port's center. This progressive change in cone angle provides two significant benefits. First, it results in a port which has a relatively shallow funnel that reduces the distance between the skin surface and the catheter valve which seals around the introduced catheter or the filament and which also serves to better orient and hold the introduced needle.
Several of the ports according to this specification also feature means for stopping the introduced needle before it reaches the catheter valve but which permits the introduced catheter to pass through the catheter valve.
The access ports in accordance with additional embodiments of this invention achieve simplicity in construction and reduce the number of components required to provide the necessary fluid seal. In those applications where it is desired to access a port using a sharp needle, damage to elastomeric sealing elements in prior port designs can occur over repeated entries to the port. In accordance with these embodiments, the implanted port has an articulating valve mechanism in which the accessing needle (or other filament) contacts a hard material, such as a metal, to open the valve. Therefore, a durable device is provided which is not damaged through long term use. The features of this embodiment are achieved through the use of an articulating valve assembly in which a sealing element is normally maintained in contact with a valve seat. When introducing an external filament, which may be a needle, catheter, wire, optical fiber etc., the filament engages the sealing element forcing it from engagement with the valve seat. Once fully inserted into the access device, features are provided to assure a fluid seal around the introduced filament.
The access ports of this invention are implanted in the same general manner as prior art devices. When the care provider desires to infuse a therapeutic agent, remove a body fluid, or have vascular access, a filament such as a catheter is introduced into the port. The entrance orifice guides the introduced catheter or needle into a proper "docking" position with the articulating valve. By pushing on the externally introduced filament, the filament is forced through the valve, thereby providing an open communication pathway for the infusion of therapeutic agents, extraction of body fluids, introduction of an optical fiber, clearing by a wire, etc. The introduced filament can be fed into the internal catheter to any extend desired. In the case of introducing a flexible catheter, a guide wire can be inserted into the external catheter to increase its rigidity. The convenient access to the port and internal catheter enables these elements to be cleared with a clearing wire avoiding the problem of permanent impaction as seen in prior art devices. In addition, the ability to feed a guide wire into the access port and internal catheter of this invention enables the internal catheter to be repositioned using a bent or "steerable" guide wire.
The access ports having an articulating valve of this invention possess the advantage that they have a very small reservoir or "dead space", meaning that virtually all of the infused fluid is put through to the desired infusion site. This invention, therefore, facilitates infusion of incompatible materials in a serial fashion since very little of the previously infused fluid remains in the device when a subsequent infusion is carried out. This invention also facilitates simultaneous infusion of incompatible materials by using a multi-lumen catheter inserted through the implanted catheter.
Another aspect of the present invention is a design for an access port which is configured such that a line normal to the plane formed by the entrance orifice is nearly at a right angle to the exit passageway. The port access opening guides an introduced filament toward and into the internal catheter. This approach of guiding a catheter to undergo a bend through the port can be used with conventional port designs having a self-sealing rubber septum. Other aspects of the present invention relate to providing a reservoir within an access port for containing an antimicrobial (or antibacterial) fluid, offering enhanced protection against introduced infection. This invention is further related to various means of securely fastening an internal catheter to an access port.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.